BOLT 6K0697 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the engine speed/timing system or if a diagnostic code in Table 1 is active.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
190-8 Engine Speed Sensor abnormal frequency, pulse width, or period The engine speed is greater than zero rpm and the pattern from the timing ring is incorrect for 5 seconds. The engine speed is set to zero rpm.
The code is active.
The code is logged if the pattern from the timing ring returns for 5 seconds.
342-8 Secondary Engine Speed Sensor abnormal frequency, pulse width, or period The Electronic Control Module (ECM) provides the engine speed/timing sensor with 12 1 VDC. The engine speed/timing sensor provides a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensors. The timing reference gear is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference gear allows the ECM to determine the crankshaft position, rotation, and rpm.If the primary engine speed/timing sensor fails, the ECM will use the secondary engine speed/timing sensor until electrical power is removed from the ECM. To prevent any unnecessary down time, repair the primary engine speed/timing sensor or replace the primary engine speed/timing sensor at the earliest possible convenience.The engine speed/timing sensor generates a pulse signal to the ECM as each tooth passes the sensor. The ECM counts the pulses in order to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern in order to determine the crankshaft position. The ECM uses this information to determine the position of the No. 1 piston. The ECM then triggers each fuel injector to fire in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM. The ECM uses engine rpm and engine load to determine the timing and duration of injection. The loss of the signal from the engine speed/timing sensor generates a diagnostic code. The loss of the signals from both of the engine speed/timing sensors triggers the termination of the signals to the fuel injectors.
Illustration 1 g03337945
Schematic for the engine speed/timing sensors and the timing calibration sensor
Test Step 1. Inspect Electrical Connectors and Wiring
Remove electrical power from the ECM.
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Location of the J1/P1 ECM connectors
(1) J1 ECM connector
Illustration 3 g01215178
Location of the engine speed/timing sensors (typical left side engine view)
(2) Secondary engine speed/timing sensor
(3) Primary engine speed/timing sensor
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Location of the timing calibration probe (typical right side engine view)
(4) Timing calibration sensor
Thoroughly inspect connectors (1). Also, thoroughly inspect the connectors for sensors (2), (3), and (4). Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Illustration 5 g03337949
P1 ECM connector
(P1-13) Secondary engine speed/timing signal
(P1-33) Primary engine speed/timing signal
(P1-40) Engine timing calibration −
(P1-41) Engine timing calibration +
(P1-43) +12.5 V supply
(P1-51) Digital return
Illustration 6 g01228872
Illustration 7 g01159881
Sensor connector
(Terminal A) Sensor supply
(Terminal B) Sensor return
(Terminal C) Signal
Perform a 45 N (10 lb) pull test